Silica zeolite low-k dielectric thin films

ABSTRACT

Thin films for use as dielectric in semiconductor and other devices are prepared from silica zeolites, preferably pure silica zeolites such as pure-silica MFI. The films have low k values, generally below about 2.7, ranging downwards to k values below 2.2. The films have relatively uniform pore distribution, good mechanical strength and adhesion, are relatively little affected by moisture, and are thermally stable. The films may be produced from a starting zeolite synthesis or precursor composition containing a silica source and an organic zeolite structure-directing agent such as a quaternary ammonium hydroxide. In one process the films are produced from the synthesis composition by in-situ crystallization on a substrate. In another process, the films are produced by spin-coating, either through production of a suspension of zeolite crystals followed by redispersion or by using an excess of the alkanol produced in preparing the synthesis composition. Zeolite films having patterned surfaces may also be produced.

BACKGROUND OF THE INVENTION

[0001] This invention relates to the provision of new low-k dielectricfilms for use in semiconductor and integrated circuit devices.

[0002] With the continuing decrease in size of microprocessors, low-kdielectrics are required to address some of the challenging problemssuch as cross-talk noise and propagation delay. These can become morecritical to performance and more difficult to overcome as overallsemiconductor device size is decreased while capabilities are increased.Among other aims, the industry is engaged in a search for dielectricshaving a lower k value than dense silicon dioxide (k=3.9-4.2). Theindustry expects that low-k dielectric materials, especially materialswith a k value lower than 3, and optimally lower than 2.2, will beneeded for the design of devices with very small, e.g., 100 nm,features. In addition to the low k value, new dielectric materials mustalso meet integration requirements. These include a thermal stability inexcess of 400° C., good mechanical properties, good adhesion to avariety of surfaces and substrates, low water uptake and low reactivitywith conductor metals at elevated temperatures.

[0003] A great number of materials have been proposed and studied aspotential candidates, including some that demonstrated k values of 2 orlower. Two major classes of such materials are dense organic polymersand porous inorganic-based materials. Some dense organic polymers (e.g.,highly fluorinated alkane derivatives such as polytetrafluoroethylene)may have sufficiently low k values, but they have the disadvantages ofhaving relatively low thermal stability, thermal conductivity, andmechanical strength. In addition there is concern that they may reactwith conductor metals at elevated temperatures.

[0004] Among porous inorganic-based low-k materials, sol-gel silica hasbeen extensively studied and is commercially available, for example fromAllied Signal or Honeywell under the trademark Nanoglass. Sol-gel silicaoffers tunable k values, but some major concerns have been cited. It hasa relatively low mechanical strength and a wide pore size distribution.Heat conductivity can be a shortcoming, especially with highly poroussol-gels, and this product also can possess a low resistance toelectrical breakdown because of some randomly occurring large pores. Inaddition, its pore surfaces are initially hydrophilic, and requiresurface treatment to avoid absorption of moisture.

[0005] Recently, surfactant-templated mesoporous silica has been studiedfor low-k dielectric applications. Such materials are described, forinstance, by Zhao, et al., Adv. Mater. 10, No. 6,1380 (1998) andBaskaran et al., Adv. Mater. 12, No. 4,291 (2000). This class ofmaterials has more uniform pores than sol-gel silica (with a range ofpore size of up to about 100 nm) and has been shown to have promising kvalues. Like sol-gel silica, however, there are concerns around lowmechanical strength and hydrophilicity.

[0006] Hydrogen silsesquioxane films have also been under considerationfor use as low-k dielectrics. Resins of this type, from which the filmsare produced, have been described in Lu et al., JACS 122, 5258 (2000)and a number of patents, including the recent U.S. Pat. No. 6,210,749. Aseries of these has recently been introduced under the trademarks FOxand XLK by Dow Corning. The FOx products are non-porous and have a kvalue of about 2.9. By incorporating porosity through a complexthree-step process involving a high boiling organic solvent and ammoniagellation, XLK films with a lower k value of about 2.0-2.3 can beproduced. Other Dow Corning products recently introduced include atrimethylsilane-containing gas (sold under the trademark Z3MS CVD) whoseapplication by chemical vapor deposition can variously produce thin filmdielectrics comprised of silicon oxycarbide or silicon carbide. Suchtechnology is described, for instance, in U.S. Pat. No. 6,159,871.However, the k values of such films do not reach the lower end of thedesirable range.

[0007] It would be advantageous, in light of these developments, toprovide a low-k dielectric material that can be applied as a thin film,has relatively small pores (most preferably <5 nm) and uniform poredistribution, with the necessary mechanical strength to be treated bychemical and mechanical polishing (CMP). Preferably, also, such filmswill have low hydrophilicity or can readily be modified to have lowhydrophilicity, so that they would be relatively unaffected by thepresence of moisture.

BRIEF SUMMARY OF THE INVENTION

[0008] This invention comprises the provision for use in semiconductordevices, of films that are comprised of silica zeolites, as well asmethods for making such films, and articles such as semiconductordevices that use or include them.

[0009] In one aspect, the invention comprises a semiconductor devicehaving a substrate and one or more metal layers or structures located onthe substrate, and further including one or more layers of dielectricmaterial, in which at least one layer of dielectric material comprises asilica zeolite.

[0010] In a second aspect the invention comprises a method for producinga silica zeolite film on a semiconductor substrate comprising formingthe film by in-situ crystallization, and, as a product, a semiconductorsubstrate or device having one or more films so produced.

[0011] In a third aspect the invention comprises a method for producinga silica zeolite film on a semiconductor substrate comprising formingthe film by spin coating, and, as a product, a semiconductor substrateor device having one or more films so produced.

[0012] In another aspect the invention comprises a method for productionof silica zeolite films having surface patterns, and, as a product, asemiconductor substrate or devices having one ore more films soproduced.

[0013] In a further aspect the invention comprises certain silicazeolite films that are novel per se.

DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 comprises three SEM micrographs of pure-silica MFI films ona silicon wafer produced by in-situ crystallization: (a) beforepolishing, top view, (b) after polishing, top view, (c) after polishing,cross-sectional view.

[0015]FIG. 2 depicts X-ray diffraction patterns for a pure-silica MFIfilm of FIG. 1 and a powder MFI sample for comparison.

[0016]FIG. 3 depicts dependence on exposure time to air with 60%relative humidity of the dielectric constant k of a calcined pure-silicaMFI film as shown in FIG. 1, and of one that has been treated bysilylation.

[0017]FIG. 4 depicts the dielectric constant as a function of frequencyfor a calcined pure-silica MFI film produced by in-situ crystallizationof the film of FIG. 1 and a film produced by spin-on of redispersed MFInanocrystals.

[0018]FIG. 5 shows the dependence of the dielectric constant (k) of anas-synthesized pure-silica MFI film of FIG. 1 on exposure time to air,with 60% relative humidity.

[0019]FIG. 6 comprises three SEM micrographs of spin-on pure-silica MFIfilms produced using a colloidal suspension of nanocrystals: (a)as-deposited, top view, (b) after microwave treatment, top view, (c)after microwave treatment, cross-sectional view.

[0020]FIG. 7 comprises four SEM micrographs of pure-silica MFI filmsproduced by spin-on of redispersed MFI nanocrystals: (a) top view of afilm with one spin; (b) cross-sectional view of a film with one spin;(c) cross-sectional view of a film with three spins (d) cross-sectionalview of a film with four spins.

[0021]FIG. 8 comprises six SEM micrographs of pure-silica MFI filmsproduced by spin-on of redispersed MFI nanocrystals that were treatedwith secondary growth by microwaves, with different treatment times.

[0022]FIG. 9 depicts IR spectra of pure-silica MFI films produced byspin-on of redispersed MFI nanocrystals that were (a) untreated and (b)treated with microwaves after production.

[0023]FIG. 10 depicts X-ray diffraction patterns for films in FIG. 9.

[0024]FIG. 11 depicts the dependence of the k value on the exposure timeto air of 60% relative humidity for a pure-silica MFI film produced byspin-on with 3 spins of redispersed MFI nanocrystals.

[0025]FIG. 12 comprises three SEM micrographs of pure-silica MFI filmsprepared by a spin-on process conducted without redispersion of zeolitecrystals.

[0026]FIG. 13 shows the dependence of the dielectric constant (k) of anas-synthesized pure-silica MFI film of FIG. 12 on exposure time to air,with 50-60% relative humidity.

[0027]FIG. 14 depicts dielectric constant as a function of frequency fora calcined pure-silica MFI film produced from the film of FIG. 12.

[0028]FIG. 15 depicts nitrogen adsorption-desorption isotherms of twobulk silica samples dried using two procedures: static drying (FIG. 15a)and flow-air drying (FIG. 15b)

[0029]FIG. 16 depicts powder X-ray diffraction patterns for bulkmaterials from a zeolite nanoparticle suspension taken at wide and lowangles.

[0030]FIG. 17 comprises four SEM micrographs showing surface-patternedsilica zeolite films.

DETAILED DESCRIPTION OF THE INVENTION

[0031] This invention relates to the production and use of thin films ofsilica zeolites in integrated circuit and semiconductor assemblies orsubstrates, and for other uses as described herein. The term “silicazeolites” refers to zeolites having only or substantially only siliconand oxygen, and very little or no aluminum or other metals typicallyfound in zeolites. For the purposes of this invention, silica zeolitescan contain minor amounts of aluminum or other metals, that is, amountsthat do not adversely affect the properties or performance of theresulting films. Silica zeolites of this type are generally referred toas “high-silica MFI zeolites”. However, it is preferred that pure-silicaMFI zeolites are used in this invention. “Pure-silica MFI zeolites” aresilica zeolites having only silicon and virtually no aluminum or othermetals. One type of pure-silica MFI zeolite preferred for use in thisinvention, known as silicalite, is described in Flanigen, et al.,Nature, 271, 512 (1978). Other silica zeolites that may be used in thisinvention include BEA, MCM-22, and MTW. Silica zeolites suitable for usein this invention may be produced either using starting materialscontaining only silicon and no metals, or may be produced bydemetallation, particularly dealumination, of zeolites that containaluminum or other metals.

[0032] Zeolites in general are microporous crystalline materials withgenerally uniform molecular-sized pores that have been described ingeneral as having low theoretical dielectric constants [e.g., Haw, etal., Nature 1997, 389, 832 and van Santen, et al., Chem. Rev. 1995, 95,637.]. Their pore size (<2 nm) is significantly smaller than sizes oftypical features of integrated circuits. Zeolites have higher heatconductivity (0.24 W/m° C.) than sol-gel silica due to their densecrystalline structure. Unlike organic polymers and inorganic-organiccomposite low-k materials, pure silica is also known for itscompatibility with current semiconductor processes.

[0033] Some types of silica zeolite films are known. The production anduses of silica zeolite films are described, for instance, in Jansen, etal., Proc. 9^(th) Intl. Zeolite Conf. (Montreal, 1992) and J. CrystalGrowth vol. 128, 1150 (1993), Koegeler et al., Studies in SurfaceScience and Catalysis, vol. 84, 307 (1994) and Zeolites 19, 262 (1997)and den Exter et al., Zeolites vol. 19, 13, (1997). They also aredescribed in a 1999 review article entitled “Zeolite Membranes” byTavolaro et al. (Adv. Mater. vol. 11, 975). At least some of these filmswere produced, for instance, by a process similar to the in-situcrystallization process described herein. However, in all thesepublications the zeolite films were prepared for uses other than insemiconductor or electronic devices - uses that are typical and knownfor zeolites, for instance as catalytic membranes, for the separation ofgases or liquids, or for chemical sensors. In some cases the films wereprepared on silicon wafers, among other types of supports. However,there is no mention in any of these publications of the suitability ofthem for use in semiconductor devices. One publication of two of thepresent inventors and others discloses production of patternedpure-silica MFI films using a stamp, with a suggestion that they may beuseful in microelectronic and optoelectronic applications [Huang et al.,J.A.C.S. vol. 122, 3530 (2000)].

[0034] In one aspect, this invention thus comprises providing asemiconductor device that comprises a semiconductor substrate, one ormore metal layers or structures, and one or more dielectric films,wherein at least one dielectric film comprises a silica zeolite film.

[0035] By “semiconductor substrate” is meant substrates known to beuseful in semiconductor devices, i.e. intended for use in themanufacture of semiconductor components, including, for instance, focalplane arrays, opto-electronic devices, photovoltaic cells, opticaldevices, transistor-like devices, 3-D devices, silicon-on-insulatordevices, super lattice devices and the like. Semiconductor substratesinclude integrated circuits preferably in the wafer stage having one ormore layers of wiring, as well as integrated circuits before theapplication of any metal wiring. Indeed, a semiconductor substrate canbe as simple a device as the basic wafer used to prepare semiconductordevices. The most common such substrates used at this time are siliconand gallium arsenide.

[0036] The films of this invention may be applied to a plain wafer priorto the application of any metallization. Alternatively, they may beapplied over a metal layer, or an oxide or nitride layer or the like asan interlevel dielectric, or as a top passivation coating to completethe formation of an integrated circuit.

[0037] At least two different processes may be used to prepare thesilica zeolite films and the semiconductor devices that include them.These are in-situ crystallization and the spin-on technique.

[0038] In both processes, a silica zeolite synthesis composition isfirst formed by combining a silica source with an organiczeolite-forming structure-directing agent (“SDA”). The silica source ispreferably an organic silicate, most preferably a C₁-C₂ orthosilicatesuch as tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate(TMOS). However, inorganic silica sources such as fumed silica, silicagel or colloidal silica, may also be used. The zeolite-formingstructure-directing agent is typically an organic hydroxide, preferablya quaternary ammonium hydroxide such as tetrapropylammonium hydroxide(TPAOH), tetraethylammonium hydroxide (TEAOH), triethyl-n-propylammonium hydroxide, benzyltrimethylammonium hydroxide, and the like. Theresulting synthesis composition contains ethanol, if TEOS is used as thesilica source, or methanol, if TMOS is used.

[0039] In the in-situ crystallization process of this invention, themolar composition of the synthesis composition is xSDA/1 silicasource/yH₂O. X can range from about 0.2 to about 0.6, preferably fromabout 0.2 to about 0.45, and most preferably 0.32. Y can range fromabout 100 to 200, preferably from about 140 to about 180 and is mostpreferably 165.

[0040] In the in-situ crystallization process, in general, the substrateto be coated is brought into contact with the synthesis compositioninside a reaction vessel such as an autoclave. The vessel is then sealedand placed in an oven. If a convection oven is used, heating isgenerally conducted at a temperature of from about 120° C. to about 190°C., preferably from about 160° C. to about 170° C. and most preferablyabout 165° C. A microwave oven can also be used, in which case the powerlevel is preferably high and the time is from 5 to 30 minutes,preferably 10 to 25 minutes, and most preferably about 10 minutes. Thedrying step is preferably followed by heating conducted at temperaturesof from about 350° C. to about 550° C., preferably from about 400° C. toabout 500° C. This heating step, usually referred to as a calcinationstep, accomplishes removal of the SDA from the film and can improve thefilm's adhesion and strength.

[0041] Films produced by this process generally have a k value of lessthan 3.3, in some cases as low as about 2.7. The film thickness isgenerally less than about 1000 nm, preferably less than about 500 nm.

[0042] The films produced by this process are generally hydrophobic;consequently, their properties are relatively uninfluenced by moisture.If desired, hydrophobicity may be increased further by removal ofsurface hydroxyl groups by silylation, for instance, withchlorotrimethylsilane, as described below, by high temperatureoxidation, or by other techniques known in the art for this purpose.

[0043] There are two embodiments of the spin-on process, one involvingredispersion of zeolite crystals, the other not involving thistechnique.

[0044] In the first embodiment, a zeolite synthesis compositioncontaining an SDA, a silica source (as described above) and water isprepared. The molar composition of the synthesis composition is x₁ SDA/1silica source /y₁ H₂O. X₁ can range from about 0.2 to about 0.5,preferably from about 0.3 to about 0.4, and most preferably 0.36. Y₁ canrange from about 5 to about 30, preferably from about 10 to about 20,and most preferably 14.29.

[0045] In conducting this process, the above synthesis composition isprepared. Then the composition is loaded in a vessel, which is sealed,and the composition is heated to a temperature of from 40 to 100° C.,preferably 60- 90° C. and most preferably 80° C. The heating time isfrom 1 day to 7 days, preferably 2-4 days, and most preferably 3 days. Asuspension of zeolite crystals is produced.

[0046] In this embodiment, the suspension is then centrifuged orotherwise treated to recover nanocrystals (i.e., nanometer-sizedcrystals). The crystals are then redispersed in ethanol or anotherappropriate dispersant, and are placed on a substrate that is situatedon a spin coater. Spin coating is then conducted as known in the art byrotating the substrate at high speeds such that a highly uniform film isobtained on the substrate. Preferably the film is subjected to a briefdrying step (e.g. about 10-12 minutes at 100° C.). Finally the film issubjected to a heating (“calcination”) step. This step is conducted attemperatures of from about 350° C. to about 550° C., preferably fromabout 400° C. to about 500° C. It accomplishes removal of the SDA fromthe film and can improve the film's adhesion and strength.

[0047] In another embodiment of the spin-on process, involving a spin-onof as-synthesized nanoparticle suspension, methanol or ethanol isincluded in the initial synthesis composition. If a lower alkylorthosilicate is used as the silica source, methanol or ethanol ischosen as corresponding to the alkyl groups. This is in addition to anyamount formed by the hydrolysis of the organic silica source. If aninorganic silica source is used, either methanol or ethanol may be used.The molar composition of the synthesis composition is x₂ SDA/1TEOS/z₂EtOH(or MeOH)/y₂ H₂O. X₂ can range from about 0.2 to about 0.5,preferably from about 0.3 to about 0.4, most preferably 0.36. Y₂ canrange from about 10 to 20, preferably from about 12 to about 18, mostpreferably 14.29. Z₂ can range from about 1 to about 10, preferably fromabout 2 to about 6, most preferably 11.2.

[0048] In this embodiment it is not necessary to collect and thenredisperse the zeolite nanocrystals, and the suspension (withoutredispersion) is subjected to spin coating as described above, followedby optional drying and then heating or calcination.

[0049] Films produced by the spin-on process of this invention generallyhave a k value of less than 3.2, and in some cases the k value may be aslow as about 2.1. The film thickness is generally less than about 800nm, preferably less than about 500 nm.

[0050] The films produced by the spin-on process of this invention arenew types of silica films that are distinct from those previouslyproduced by Jansen and others and described in the publicationsmentioned above. Those films produced in the past were often notcompletely continuous. However, even when successfully produced ascontinuous films, they had (as is typical for zeolites) a single,relatively uniform, pore size—an average pore size of about 5.5Angstroms (this size was generally referred to as “micropores”), Thetotal porosity of such films (ratio of pore volume to total film volume)was about 30-33%

[0051] On the other hand, films produced by both embodiments of thespin-on process described herein are continuous bimodal films, havingboth micropores, as defined above, and larger pores, generally termedmesopores. These films are novel per se, and may be used not only insemiconductor structures as described herein, but also for other usesknown for zeolite films such as catalytic membranes, separation of gasesor liquids, and chemical sensors.

[0052] The micropores of these novel films have an average pore size ofabout 5.5 Angstroms and a total pore volume of from about 0.15 to about0.21 cm³/g. The mesopores have an average pore size of from about 2 toabout 20 nm, preferably from about 2 to about 10 nm, most preferablyabout 3 nm. Total pore volume of the mesopores is from about 0.1 toabout 0.45 cm³/g, preferably from about 0.2 to about 0.3 cm³/g, and mostpreferably about 0.25 cm³/g. The total porosity of these novel films isabout 50%.

[0053] When the zeolite precursor or synthesis composition is formedusing excess ethanol or methanol, as above, the resulting suspension mayalso be used to produce silica zeolite films having surface patterns.Ethanol is preferred for this process. Here, instead of in-situcrystallization or spin coating, the suspension is simply deposited onan appropriate substrate and allowed to dry at ambient temperatures.Surface patterns are believed to form spontaneously as a result ofconvection due to the evaporation of the excess ethanol. Eventually thesuspension dries completely, and the zeolite nanoparticles become lockedinto solid patterns. The use of ethanol as opposed to another alcoholsuch as propanol, the presence of excess ethanol in the system (asopposed to only the amount generated between the template and the silicasource), and the crystal size in the suspension, are important factorsin the production of surface-patterned silica zeolite films by thisprocess. Preferably, the suspension contains crystals of about 25-50 nmdiameter, as well as smaller nanoslabs and nanoslab aggregates.

[0054] Patterned films produced by the above process are not necessarilydisposed in very thin layers, because they have not undergone steps suchas spin-on coating to render them so. In addition, they do notnecessarily possess k values as low as other films described herein.However, they are considered useful for electronic and otherapplications.

[0055] As described below, the properties of silica zeolite filmsproduced by spin-coating can be varied in several ways. The filmthickness can be increased, if desired, by conducting the spin-onprocess two or more times, with additional material added on eachoccasion. If the film is produced by the first embodiment of the spin-onprocess, that is, one in which crystals are redispersed before thespin-on is conducted, the adhesion of the film to the substrate may notbe strong enough to withstand treatments such as mechanical polishing.If that is the case, the calcined film can be treated by exposing it tomicrowaves in the presence of additional zeolite synthesis or precursorsolution, or by heating it with additional zeolite precursor solution ina convection oven or similar equipment. This produces a secondary growthof zeolite on the substrate, but if the treatment is kept reasonablybrief (perhaps less than 15 minutes for microwaving), the film thicknessdoes not significantly increase.

[0056] The films produced by the spin-on processes also are generallyhydrophilic. To minimize or prevent adverse affects due to moisture,these films may be made substantially hydrophobic by treatments toremove surface hydroxyl groups, such as by silylation (withchlorotrimethylsilane, for example), high temperature oxidation, orother techniques known in the art for this purpose.

[0057] The following examples are provided to illustrate the invention.However, these examples are included as illustrative only, and not withthe intention or purpose of limiting the invention in any way.

EXAMPLE 1

[0058] This example illustrates an in-situ crystallization process forproduction of pure-silica MFI films and describes properties of thefilms so produced.

[0059] Thin (controllable between 250-500 nm) b-oriented pure-silica MFIfilms were prepared on a silicon wafer by in-situ crystallization usinga clear synthesis composition with the molar composition being0.32TPAOH: TEOS: 165H₂O (TPAOH=tetrapropylammonium hydroxide;TEOS=tetraethylorthosilicate). A clean-room grade wafer was used,without further cleaning. The wafer (2×2 cm) was fixed in a Teflon-linedParr autoclave. Crystallization was carried out in a convection oven at165° C. for 2 hours. As-synthesized film samples were rinsed withdeionized water and blow-dried with air. Removal of the organicstructure- directing agent (tetrapropylammonium hydroxide) was carriedout by calcination at 450° C. for 2 h under air. Pure-silica MFI thinfilms of equal quality were successfully prepared on low-resistivitysilicon (for capacitance measurement), high resistivity silicon (fortransmission FT-IR measurement), silicon nitride and silicondioxide-covered wafers.

[0060]FIG. 1 shows SEM micrographs of a pure-silica MFI film produced byin-situ crystallization on a low resistivity silicon wafer. The film iscontinuous, and predominantly b-oriented (FIG. 1a). The orientation ofthe film was confirmed by x-ray diffraction (FIG. 2). Some twinnedpure-silica MFI crystals are present. These can cause minor surfaceroughness. However, a smooth surface can be obtained by simple polishingfor about 10 min with 0.05 μm alpha-Al₂O₃ suspension using a Buehlerpolisher. The polished film (FIG. 1b) is shiny and shows a uniformcharacteristic green color consistent with its thickness. No crack orfilm delamination was observed during polishing, indicating that thefilm has excellent mechanical strength and adhesion, and is potentiallycompatible with chemical mechanical polishing (CMP). A cross-sectionalSEM micrograph shows that the polished film has a uniform thickness of320 nm (FIG. 1c).

[0061] The pure-silica MFI film so obtained has an elastic modulus of30-40 GPa (by nanoindentation). The modulus of sol-gel based films, onthe other hand, is often less than 6 GPa. A modulus of 6 GPa is usuallyconsidered a threshold value for low-k dielectrics. The modulus ofmesoporous silica has been reported to be in the range of 14-17 GPa fora porosity of ˜55% and it is expected that the modulus will decreasewith porosity. Dense silica has a modulus of about 70 GPa.

[0062] To measure the dielectric constant of the film, aluminum dotswith a diameter of 1.62 mm and a thickness of 1 μm were deposited on apolished pure-silica MFI film using thermal evaporation depositionthrough a shadow mask. The reverse side of the sample was etched withbuffered hydrofluoric acid to remove pure-silica MFI film; then a layerof aluminum was deposited by evaporation. The dielectric constant of thepure-silica MFI film was calculated by measuring the capacitance of theaforementioned metal-insulator-metal structure using a Solartron 1260impedance analyzer combined with standard Signatone probe station andmicropositioner. Four aluminum dots were usually deposited and theaverage k value reported. The film sample was dried at 120° C. overnightand saved in a desiccator before capacitance measurement. A dry nitrogenblanket was also applied during capacitance measurement to minimizewater adsorption. As-synthesized and calcined films were shown to havedielectric constant values of 3.4 and 2.7 and dielectric loss tangentsof 0.013 and 0.018 at 1 MHz, respectively. There is little change of kversus frequency at around 1 MHz (FIG. 4). The k value of the calcinedfilm is consistent with the known porosity of pure-silica MFI (33%).

[0063] The effect of water adsorption on the k value of a pure-silicaMFI film prepared by this process was examined by exposing the sample toair at 60% relative humidity and monitoring the k value versus exposuretime. As expected, there is no change of the k value with exposure time(FIG. 5).

[0064] Transmission FT-IR (Bruker Equinox 55) measurements wereconducted on pure-silica MFI films prepared on a high-resistivity wafer.Only a very weak water adsorption band was detected in the calcinedsamples; this is consistent with the k value measurement.

EXAMPLE 2 Spin-coating with Redispersed Zeolite Nanocrystals

[0065] To reach ultra-low k values, the porosity of a pure-silica MFIfilm can be increased using spin-coating, a process that the currentsemiconductor industry regards as more friendly than in-situcrystallization. This type of silica zeolite film has a higher porosityowing to the presence of inter-nanocrystal packing voids.

[0066] Pure-silica MFI nanocrystals were prepared by the procedurereported in Huang, et al., above; Wang, et al., Chem. Commun., 2333(2000), as follows. A synthesis composition was prepared by dropwiseaddition of aqueous TPAOH solution into TEOS with strong agitation,followed by 3 days of aging at 30° C. under stirring. The molarcomposition of the final clear solution was 0.36 TPAOH: TEOS: 14.29 H₂O.The clear solution was loaded into a polypropylene bottle and heated at80° C. for 3 days, with constant stirring at 250 rpm. The resultingcolloidal nanocrystals were recovered by repeated cycles ofcentrifugation at 15,000 rpm. The centrifugate was recovered afterdecanting the upper solution, and the product was redispersed in purewater under ultrasonic treatment. The cycle was repeated until thesupernatant liquid had a pH<8. Finally the product was redispersed inethanol for use in spin coating. Nanocrystals so obtained have a uniformdiameter of about 50 nm. A Laurell spin coater was used, with a spinrate of 3000 rpm.

[0067] During the spin coating, the pure-silica MFI nanocrystalsself-assembled into a uniform film. This is thought to be a result ofhydrogen bonding of pure-silica MFI surface hydroxyl groups whileethanol was evaporated. SEM images show that the films thus producedhave a smooth surface with a close-packed structure (FIG. 6a) and auniform thickness of 290 nm . The film thickness can be controlled byadjustment of the solid loading of the suspension. The film was calcinedat 450° C. for 2 h to remove the organic structure-directing agent. N₂adsorption was performed on bulk material obtained using a similardrying procedure and revealed that the film had a uniform inter-particleparticle pore size of 17 nm and inter-particle pore volume of 0.40cm³/g. Capacitance measurement showed that calcined spin-on films have ak value of 1.8-2.1, namely one that reaches the ultra low-k range. Thedielectric loss tangent of these films is about 0.0075. The k valuechanges little with frequency at around 1 MHz

EXAMPLE 3 Variation in Spin Number

[0068] Experiments were conducted to determine the effect on filmthickness of conducting the spin-on process several times in successionwith a further quantity of synthesis composition added each time. FIG. 7contains SEM micrographs of the top and cross-sectional views of spin-onfilms. FIG. 7(a) is the top view of a film produced by a single spin-on.FIG. 7(b) is a cross-sectional view of the same film. FIGS. 7(c) and7(d) are cross-sectional views of films produced by three and fourspin-ons, respectively. The SEM micrographs show that the spin-on filmof nanocrystals had a smooth surface with a close-packed structure (FIG.7a). The film thickness is uniform and can be controlled by adjustmentof the number of spin-ons. The film thickness was 240, 420 and 540 nmcorresponding to the spin-on number of 1, 3 and 4, respectively.Alternatively the film thickness may be controlled by adjustment of theconcentration of nanocrystals in the ethanol solution.

EXAMPLE 4 Secondary Growth by Microwave Treatment of Films Prepared bySpin-coating of Redispersed MFI Nanocrystals Suspension

[0069] Although calcination apparently improves bonding strength amongnanocrystals through condensation/cross-linking of surface hydroxyls,the films produced by spin-on of redispersed crystals may not be adheredstrongly enough to the wafer to withstand mechanical polishing. Inaddition, the existence of large inter-particle mesopores fromnanocrystal packing can be of concern for practical applications. Abrief secondary growth of pure-silica MFI nanocrystals can be conducted,if it is desired to reduce mesopore size, by treating the spin-on filmwith a silicate precursor solution in a microwave oven.

[0070] Microwave treatment of the spin-on pure-silica MFI films using asolution of 0.32TPAOH: TEOS: 165H₂O was carried out in a Sharp householdmicrowave oven (700 W). Five grams of solution was used in eachtreatment. The spin-on film was placed horizontally in a 45 mLTeflon-lined Parr autoclave (for microwave use). Power level 1 (10%) wasused. Microwave-treated films were rinsed with deionized water,flow-dried with air and calcined at 450° C. for 2 h under air.

[0071]FIG. 8 shows SEM top and cross-sectional micrographs ofpure-silica MFI films with different microwave treatment times. Film #1(FIGS. 8a and 8 b) was prepared with spin-coating for three times, thentreated in a microwave for 8 minutes. Film #2 (FIGS. 8c and 8 d) wasprepared by a single spin-coating, then microwaved for 10 minutes. Film#3 (FIGS. 8e and 8 f) was prepared by a single spin-coating, thenmicrowaved for 15 minutes. The SEM images clearly show that the filmsbecame more compact after microwave treatment and that the compactnessincreased with increasing time of microwave treatment. Therefore, itappears that the porosity of these films can be controlled by changingthe microwave treatment time. When the microwave treatment time wasshorter than 15 minutes, the final film thickness remained unchanged(compare FIGS. 7b and 8 d, and FIGS. 7c and 8 b). When the microwavetreatment time was to 15 minutes, the film became thicker compared tothat of the film that had not been microwaved (compare FIGS. 7b and 8f). It was observed that no crystals formed in the bulk phase when themicrowave treatment time was shorter than 15 minutes, while formation ofcrystals was noticed in the bulk phase when the microwave treatment timewas longer than 15 minutes. These results indicated that the secondarygrowth proceeds initially by local epitaxy on the deposited nanocrystal(e.g. within 10 minutes), and that later in the process, depositionproceeds by incorporation of particles from the solution, together withre-nucleation on the growing film (e.g. longer than 15 minutes).

[0072] The SEM images clearly show that inter-crystal voids are reducedby secondary growth (see FIG. 8b). A polishing experiment indicated thatthe mechanical properties of the final film had been significantlyimproved. Under microwave treatment, the secondary growth producesmaterials primarily within the nanocrystal matrix, and therefore thefinal film thickness remains unchanged at 290 nm (FIG. 8c). The calcinedfilm exhibits a k value of 3.0, which is close to that of the in-situcrystallized film.

[0073] IR spectra of spin-on-only film (“a”) and microwave treated (8minutes) film (“b”) are shown in FIG. 9. It is clear from the figurethat the intensity of the characteristic framework vibration ofpure-silica MFI increased due to microwave treatment. The resultconfirmed a secondary growth of spin-on film. Similar results wereobtained from X-ray analyses of the films. FIG. 10 shows X-raydiffraction patterns of spin-on film before (“a”) and after 8 minutes ofmicrowave treatment (“b”). This figure clearly indicates increasingcrystallinity of the spin-on film due to a secondary growth duringmicrowave treatment.

[0074] Nitrogen adsorption performed on air-dried nanocrystals after asimilar microwave treatment (e.g., 8 min) as applied to the spin-on filmrevealed a uniform inter-particle pore size of 22 nm and mesoporousvolume of 0.34 cm³/g. After 4 cycles of 8 min treatment, a uniforminter-particle pore size of 3 nm and an inter-particle pore volume of0.08 cm³/g were obtained. Thus the pore size and volume can also beadjusted by changing the cycle number of microwave treatment.

[0075] Polishing experiments indicated that the microwave-treated filmstrongly adhered to the substrate. The microwave-treated (8 min),calcined film exhibited a k value of 3.0 when a normal treatment wasapplied to wash the film. However, the same film (spin-on film #1)exhibited a much lower k value of 2.4 when it had been washed byimmersing in deionized water for 2 days after microwave treatment.

EXAMPLE 5 Effect of Moisture on Zeolite Films

[0076] To study the effect of moisture on the k value, films that wereuntreated and that were treated by silylation to improve hydrophobicitywere exposed to ambient air with 60% relative humidity. It has beenreported that vapor phase silylation of pure-silica MFI film can be usedto increase the hydrophobicity of the film. The change in k value wasmonitored against the exposure time.

[0077] Silylation (vapor phase) of pure-silica MFI films produced by thespin-on process with redispersed crystals was conducted at 300° C. for 1h using gaseous chlorotrimethylsilane obtained by bubbling nitrogenthrough chlorotrimethylsilane at room temperature. Prior to silylationthe film was dehydrated at 300° C. for 5 h under a flow of nitrogen.After silylation, the system was kept under nitrogen flow at 300° C. foranother 3 h to remove unreacted chlorotrimethylsilane from the film.

[0078]FIG. 11 shows the effect of moisture on the spin-on films. Thefilm thickness was 420 nm. No significant change of k value withexposure time was seen for an as-synthesized sample. This was expectedbecause of the absence of microporosity. The k value was found to bearound 2.2. The k value for a calcined sample increased moderately from2.1 to 3.2 (i.e., 50% increase) within an exposure time of 1 hour. Therewas no significant change in the k value with exposure time for asilylated film, and the k value (1.8) was in the ultra low-k range.Microwave-treated film #1 had a k value of 2.2 after silylation.

[0079] The effect of moisture on in-situ crystallized pure-silica MFIfilm also was studied. As expected, there was no significant change ofthe k value with exposure time for an as-synthesized sample because ofits hydrophobicity and nonporous nature. The k value for a calcinedsample increased moderately from 2.7 to 3.3 (i.e., 22% increase) withinan exposure time of 30 hours (FIG. 12). The k value eventually rose to3.5 after several days. By contrast, moisture is known to have apronounced effect on sol-gel silica and mesoporous silica that has notundergone dehydroxylation treatments (e.g., the k value of mesoporoussilica increases more than 100% after exposure to moist air). Thisclearly shows that the pure-silica MFI films are more hydrophobic thansol-gel silica and mesoporous silica. FIG. 12 shows the dependence ofthe k value on the exposure time for the silylated sample of in-situcrystallized film. The increase of the k value slowed down aftersilylation, and the k value was lower than that of a calcinednon-silylated film having the same exposure time.

EXAMPLE 6 Production of Spin-on Films with As-synthesized ZeoliteNanoparticle Suspension

[0080] This example illustrates the production of a silica zeolite filmby the spin-on process, but without conducting separation andredispersion of the zeolite nanocrystals. Instead, this step is avoidedby conducting the zeolite production step in the presence of addedethanol or other alcohol that is produced during the reaction. In thisexample, a zeolite pure-silica MFI nanoparticle suspension with a rangeof particle sizes was synthesized hydrothermally as in Example 1, withthe difference that the molar composition of the synthesis compositionwas 0.36 TPAOH/1 TEOS/4 EtOH/ 14.9 H₂O. It is noted that completein-situ hydrolysis of TEOS would produce 4 moles of ethanol, so that anequal molar amount of ethanol was added deliberately to the synthesiscomposition. The clear solution thus obtained was aged at ambienttemperature for 3 days followed by heating in a capped plastic vessel at80° C. for 3 days. Stirring was provided for both the aging and theheating process. The resulting colloidal suspension was cooled to roomtemperature under stirring.

[0081] The nanoparticle suspension was then centrifuged at 5000 rpm for20 min to remove large particles, then spun on low resistivity siliconwafers. A Laurell spin coater was used; the spin rate was 3300 rpm for30 sec. The film was heated in a flow of air at 1° C./min to 450° C. andheld at that temperature for 3 h to bake the film and to remove theorganic structure-directing agent (TPA).

[0082]FIG. 12 contains SEM micrographs of the films. The as-depositedfilms were fairly smooth (FIG. 12a). The smoothness could be improved bya brief polishing with 0.05 μm alumina suspension using a Buehlerpolisher (FIG. 12b). No cracking or film delamination was observedduring polishing, indicating good mechanical strength of the film and astrong adhesion to the silicon wafer. The film was about 0.33 μm thick(FIG. 12c).

[0083] Measurements of elastic modulus and hardness were performed usinga Nano Indenter® XP and MTS' Continuous Stiffness Measurement (CSM)technique. With this technique, each indent gives the hardness andelastic modulus as a continuous function of the indenter's displacementinto the sample. Loading was controlled such that the loading ratedivided by the load was held constant at 0.05/sec. Experiments wereterminated at a depth of 300 nanometers. Ten indentations were performedon each sample. Data from the 10 indents on each sample were averaged.The elastic modulus at 10% penetration was 16-18 GPa for a 0.42 mm-thickfilm.

[0084] The dielectric constant of the film was measured using thermalevaporation deposition (Denton Vacuum DV-502) through a shadow mask.Dielectric constant was calculated by measuring capacitance of ametal-insulator-metal structure as before. Capacitance measurements showthat calcined spin-on film has a k value of 2.3. The dielectric losstangent of the film is about 0.02. The k value changes little withfrequency at around 1 MHz (FIG. 14).

[0085] The films were exposed to ambient air with 50-60% relativehumidity to study the effect of moisture adsorption. Change in the kvalue was monitored against the exposure time. The k value increasedfrom 2.3 to 3.9 (i.e., 70% increase) within an hour of exposure.

[0086] To increase hydrophobicity of the film, vapor phase silylationwas conducted as before. The silylated film had a k value of 2.1, i.e.,in the ultra low-k range. There was only a slight increase in the kvalue with exposure time (FIG. 13b).

[0087] For low-k applications, it is important to examine the porosityand pore size distribution of the porous film. FIG. 15 shows nitrogenadsorption-desorption isotherms of two bulk silica samples that havebeen dried with two different procedures. Results of detailed analysisof the isotherms are summarized in Table 1. Clearly both materials havebimodal pore size distribution (e.g., micropore at 0.55 nm and mesoporeat about 2.7-2.8 nm). TABLE 1 Results of N₂ adsorption for bulkmaterials from pure-silica MFI nanoparticle suspension. All materialscalcined under a flow of air at 450° C. for 3 hours Micro- Meso- Crys-Dry- Micro- pore Meso- pore tal- ing pore volume pore volume TotalTheoret- linity con- size (cm³/g) size (cm³/g) Porosity ical k (%)dition (nm) [a] (nm) [b] (%) [c] [d] [e] Static 0.55 0.17 2.63 0.18 2.42.4 64 dry- ing Flow- 0.55 0.17 2.81 0.25 2.2 2.2 64 air dry- ing

[0088] It also appears that drying conditions affect the porositysignificantly and thus an appropriate drying procedure should be used.Specifically, drying under convection generates more mesoporosity (0.25vs. 0.18 cm³/g). This result is reasonable if one considers thatconvection induces fast drying, during which the suspension quicklyloses fluidity so that the particles settle in position quickly, leadingto higher mesoporosity. The predicted k value for the silica driedconvectively from Bruggeman's effective medium approximation [Morgan etal., Ann. Rev. Mater. Sci., 30, 645, 2000] is closer to the measured kvalue (2.2 vs. 2.1), suggesting that the silica materials obtained fromconvective drying is more representative of the spin-on film.

[0089] X-ray diffraction (XRD) and infrared spectroscopy (IR) have alsobeen used to characterize the porous silica. Wide angle X-raydiffraction (XRD) pattern suggests the existence of silicalite structureas well as amorphous silica (see FIG. 16). Low angle X-ray diffractionpattern of the material (see Supplementary FIG. 2b) shows a poorlydefined peak at 2θ≈0.83 (d=10.64 nm), probably due to the presence ofmesopores owing to close packing of nanoparticles in the material. FT-IRspectrum (absorption band at about 550 cm⁻¹, not shown) also indicatesthe presence of pure-silica MFI zeolite structure and the crystallinityis estimated to be around 64% by using the intensity ratio of absorptionbands at 550 and 450 cm⁻¹.

EXAMPLE 7 Production of Surface-patterned Film

[0090] Two batches of a zeolite pure-silica MFI nanoparticle suspensionwith a range of particle sizes were synthesized hydrothermally as inExample 6. One batch (“Batch A”) was then heated at 70° C. for 9 days;the other (“Batch B”) was heated at 80° C. for 3 days. The resultingsuspensions were cooled to room temperature with stirring, and droppedonto horizontal clean-room grade silicon wafers, forming a liquid filmabout 2 mm thick, having a diameter of 2 cm. Drying at ambienttemperatures produced surface patterns of the knotted-rope type in thefilm of Batch A and of the wrinkled-honeycomb type in Batch B. SEMmicrographs of the films are shown in FIG. 17. The cells were slightlyirregular in shape, and the edges were highly wrinkled. Nitrogendesorption measurements showed high Brunauer-Emmett-Teller surface areasfor both films, and narrow pore size distributions for both, in both themicropore and mesopore regions.

What is claimed is:
 1. A semiconductor device comprising a semiconductorsubstrate, one or more metal layers or structures located on saidsubstrate, and one or more dielectric films, wherein at least onedielectric film comprises a silica zeolite.
 2. A process for productionof a silica zeolite film on a semiconductor substrate, comprising: (a)combining a silica source selected from organic silica sources andinorganic silica sources with an organic hydroxidezeolite-structure-directing agent (SDA) and water to produce a zeolitesynthesis composition containing the structure-directing agent, thesilica source and water, in a molar ratio of x SDA; 1 silica source: yH₂O, wherein the value of x is from about 0.2 to about 0.6 and the valueof y is from about 100 to about
 200. (b) contacting the substrate to becoated with the synthesis composition; and (c) heating the substrate andsynthesis composition from step (b) to produce a silica zeolite film onthe substrate.
 3. A process according to claim 2 in which the value of xis from about 0.2 to about 0.45 and the value of y is from about 140 toabout
 180. 4. A process according to claim 2 in which the value of x is0.32 and the value of y is
 165. 5. A process according to claim 2 inwhich the silica source is a C₁-C₂ alkyl orthosilicate.
 6. A processaccording to claim 2 in which the silica source is selected from fumedsilica, silica gel and colloidal silica.
 7. A process according to claim2 in which the structure-directing agent is a quaternary ammoniumhydroxide.
 8. A process according to claim 2 in which the silica sourceis ethyl orthosilicate and the structure-directing agent istetrapropylammonium hydroxide.
 9. A process according to claim 2 furthercomprising (d) heating the substrate and film of step (c) to atemperature of from about 350 to about 550° C.
 10. A process accordingto claim 2 further comprising treating the silica film of step (d) toremove surface hydroxyl groups therefrom.
 11. A process according toclaim 2 in which the silica zeolite is a high-silica MFI zeolite.
 12. Aprocess according to claim 2 in which the silica zeolite is apure-silica MFI zeolite.
 13. A process according to claim 2 in which thesemiconductor substrate is a silicon wafer or a gallium arsenide wafer.14. A process according to claim 2 in which the substrate comprises asilicon wafer or a gallium arsenide wafer and one or more metal layersor structures located on said wafer.
 15. A semiconductor substratehaving at least one silica zeolite film thereon produced by a processaccording to claim
 2. 16. A semiconductor substrate according to claim16 in which the at least one silica zeolite film is a pure-silicazeolite film.
 17. A process for the production of a silica zeolite filmon a semiconductor substrate, comprising: (a) combining a silica sourceselected from organic silica sources and inorganic silica sources withan organic hydroxide zeolite-structure-directing agent (SDA) and waterto produce a zeolite synthesis composition containing thestructure-directing agent, the silica source and water in a molar ratioof x₁ SDA: 1 silica source: y₁ H₂O, wherein the value of x₁ is fromabout 0.2 to about 0.5 and the value of y₁ is from about 5 to about 30;(b) heating the composition of step (a) to produce an aqueous colloidalsuspension of silica zeolite crystals; (c) separating the crystals fromthe product of step (b) (d) dispersing the separated crystals from step(c) in a dispersing agent to form a suspension of the crystals in thedispersing agent, (e) depositing the crystal suspension of step (d) on asemiconductor substrate; and (f) rotating the substrate from step (e)under conditions so as to produce a silica zeolite film thereon byspin-coating.
 18. A process according to claim 17 in which the value ofx₁ is from about 0.3 to about 0.4 and the value of y₁ is from about 10to about
 20. 19. A process according to claim 17 in which the value ofx₁ is 0.36 and the value of y₁ is 14.29.
 20. A process according toclaim 17 in which the silica source is a C₁-C₂ alkyl orthosilicate. 21.A process according to claim 17 in which the silica source is selectedfrom fumed silica, silica gel and colloidal silica.
 22. A processaccording to claim 17 in which the structure-directing agent is aquaternary ammonium hydroxide.
 23. A process according to claim 17 inwhich the silica source is ethyl orthosilicate and thestructure-directing agent is tetrapropylammonium hydroxide.
 24. Aprocess according to claim 17 further comprising (g) heating the film ofstep (f) to a temperature of from about 350 to about 550° C.
 25. Aprocess according to claim 24 further comprising treating the silicafilm of step (g) to remove surface hydroxyl groups therefrom.
 26. Aprocess according to claim 17 in which the silica zeolite is ahigh-silica MFI zeolite.
 27. A process according to claim 17 in whichthe silica zeolite is a pure-silica MFI zeolite.
 28. A process accordingto claim 17 in which the semiconductor substrate is a silicon wafer or agallium arsenide wafer.
 29. A process according to claim 17 in which thesubstrate comprises a silicon wafer or a gallium arsenide wafer and oneor more metal layers or structures located on said wafer.
 30. Asemiconductor substrate having at least one silica zeolite film thereonproduced by a process according to claim
 17. 31. A semiconductoraccording to claim 30 wherein the at least one silica zeolite film is apure-silica MFI zeolite film.
 32. A process for the production of asilica zeolite film on a semiconductor substrate, comprising: (a)combining a silica source selected from organic silica sources andinorganic silica sources with an organic hydroxidezeolite-structure-directing agent (SDA), water, and an alkanol selectedfrom ethanol and methanol, to produce a zeolite synthesis compositioncontaining the structure-directing agent, silica source, water andalkanol in a molar ratio of x₂ SDA: 1 silica source: y₂ H₂O: z₂ alkanol,wherein the value of x₂ is from about 0.2 to about 0.5, the value of y₂is from about 10 to about 20, and the value of z₂ is from about 1 toabout 30; (b) heating the composition of step (a) to produce an aqueouscolloidal suspension of silica zeolite crystals; (c) depositing thecrystal suspension of step (b) on a semiconductor substrate; and (d)rotating the substrate from step (c) under conditions so as to produce asilica zeolite film thereon by spin coating.
 33. A process according toclaim 32 in which the value of x₂ is from about 0.3 to about 0.4, andthe value of y₂ is from about 12 to about
 18. 34. A process according toclaim 32 in which the value of x₂ is 0.36, the value of y₂ is 14.29, andthe value of z₂ is 11.2.
 35. A process according to claim 32 in whichthe silica source is a C₁-C₂ alkyl orthosilicate.
 36. A processaccording to claim 32 in which the silica source is selected from fumedsilica, silica gel and colloidal silica.
 37. A process according toclaim 32 in which the structure-directing agent is a quaternary ammoniumhydroxide.
 38. A process according to claim 32 in which the silicasource is ethyl orthosilicate, the template is tetrapropylammoniumhydroxide, and the alkanol is ethanol.
 39. A process according to claim32 further comprising (e) heating the film of step (d) to a temperatureof from about 350 to about 550° C.
 40. A process according to claim 39further comprising treating the silica film of step (e) to removesurface hydroxyl groups therefrom.
 41. A process according to claim 32in which the silica zeolite is a high-silica zeolite.
 42. A processaccording to claim 32 in which the silica zeolite is a pure-silica MFIzeolite.
 43. A process according to claim 32 in which the semiconductorsubstrate is a silicon wafer or a gallium arsenide wafer.
 44. A processaccording to claim 32 in which the substrate comprises a silicon waferor a gallium arsenide wafer and one or more metal layers or structureslocated on said wafer.
 45. A semiconductor substrate having at least onesilica zeolite film thereon produced by a process according to claim 32.46. A semiconductor substrate according to claim 45 in which the atleast one silica zeolite film is a pure-silica MFI zeolite film.
 47. Aprocess for producing a patterned silica zeolite film on a semiconductorsubstrate, comprising: (a) combining a silica source selected fromorganic silica sources and inorganic silica sources with an organichydroxide zeolite-structure-directing agent (SDA), water, and an alkanolselected from ethanol and methanol, to produce a zeolite synthesiscomposition containing the structure-directing agent, silica source,water and alkanol in a molar ratio of x₃ SDA: 1 silica source: y₃ H₂O:z₃ alkanol, wherein the value of x₃ is from about 0.2 to about 0.5, thevalue of y₃ is from about 10 to about 20, and the value of z₃ is fromabout 1 to about 30; (b) heating the composition of step (a) to producean aqueous colloidal suspension of silica zeolite crystals; (c)depositing the crystal suspension of step (b) on a semiconductorsubstrate; and (d) drying the crystal suspension at ambient temperatureto produce a patterned silica zeolite film.
 48. A process according toclaim 47 in which the value of x₂ is 0.36, the value of y₂ is 14.29, andthe value of z₂ is 11.2.
 49. A process according to claim 47 in whichthe silica source is a C₁-C₂ alkyl orthosilicate.
 50. A processaccording to claim 47 in which the structure-directing agent is aquaternary ammonium hydroxide.
 51. A process according to claim 47 inwhich the silica source is ethyl orthosilicate, the template istetrapropylammonium hydroxide, and the alkanol is ethanol.
 52. A processaccording to claim 47 in which the silica zeolite is a high-silicazeolite.
 51. A process according to claim 47 in which the silica zeoliteis a pure-silica MFI zeolite.
 52. A process according to claim 47 inwhich the semiconductor substrate is a silicon wafer or a galliumarsenide wafer.
 53. A process according to claim 47 in which thesubstrate comprises a silicon wafer or a gallium arsenide wafer and oneor more metal layers or structures located on said wafer.
 54. Asemiconductor substrate having at least one patterned silica zeolitefilm thereon produced by a process according to claim
 47. 55. Asemiconductor substrate according to claim 54 in which the at least onepatterned silica zeolite film is a pure-silica MFI zeolite film.
 56. Acontinuous bimodal silica zeolite film having a pore volume of fromabout 0.15 to about 0.21 cm³/g of micropores having an average pore sizeof about 5.5 Angstroms and a pore volume of from about 0.1 to about 0.45cm³/g of mesopores having an average pore size of between about 2 andabout 20 nm.
 56. A film according to claim 56 in which the mesoporeshave an average pore size of from about 2 to about 10 nm.
 57. A filmaccording to claim 56 in which the mesopores have an average pore sizeof about 3 nm.
 58. A film according to claim 56 in which the pore volumeof the mesopores is from about 0.2 to about 0.3 cm³/g.
 59. A filmaccording to claim 56 in which the total porosity is about 50%.
 60. Asemiconductor substrate having at least one film according to claim 56thereon.